Electrical condenser and method of making same



Dec. 13, 1932. DANZGER 1,891,080

ELIEGTRICAL CONDENSER AND METHOD OF MAKING SAME Filed Dec. 26, 1928 mvsmoa flamldl ZTTORNEY Patented Dec. 13, 1932 arms I raran'r .,-HAROLD '1. minzrena, or NEW YORK, N. Y.

- ELECTRICAL connnnsnn AND METHOD ermine sm'n 1 Application filed' December 26, 1928. Serial No. 328,338.

My pres'ent invention relates generally to electricalcondensers, and has particular reference to the fixed variety wherein layers of conducting material are arranged in alternate relationship with respect to layers of insulating material.

Be'fore describing the details of my present'invention, I will premise that one type of condenser body of'the'character to which my invention relates is constructed byinterwinding, in' coiled relationship,strips of conducting material such as foil, and strips of insulating material such as paper, the e11- tire body being subjected to suitable heat 5 and'vacuum treatment to expel the air and moisture'therefrom, and being thereupon impregnated with a suitable dielectric material, such as wax or.oil.

A general-object of my invention-is'to provide a condenser of the foregoing character and amethod of manufacturing the same whereby the cost of manufactureis reduced and whereby the eniciency and life of the condenser, and its capability ofwithstand- 5 ing-the application-ofrelatively .high voltages, isincreased.

One of the purposes of the paper customarily employed in interposition between the foil layers has been to separate such layers 3 in insulated relationship in a positive manner. The ideal type of condenser, however, would dispense with such paper entirely, for a number of reasons. In. the first place, the dielectric qualities of wax or oil, heretofore 5 associated with the paper by impregnation, are superior to the dielectric qualities of the paper itself. In the second place, the employment of paper necessitates very careful preliminary treatment to remove entrained .1 gases and moisture, and even the most painstaking treatment cannot remove every vestige of such substances. In the third place, the nature and constituency of'paper renders the same conducive to the gradual development of leakage current paths therethroug'h. In the fourth place, a breakdown caused by the gradual and continued passage of a leakage current through the paper usually causes the same to char, producing a tear or opening with carbonized edges, the latter projecting in various directions out of the plane o'f the paper and facilitating the furtherpassage'of leakage currents. I I

The employment of paper has heretofore been deemed particularly necessary in cases where the impregnating medium -is a liquid such as oil, for in such an event the hardene ing characteristic of'wax or the like'is absent and there is danger of't11e foi1 layers'contacting with one another. Oil has a nuinber of advantages over wax as animpregnating medium, among which is the fact thatthe liquid character of the oil facilitates the dis'si pation of heat, thereby serving in a measure to prevent the disastrous efli'ec ts of ch'arring previously referre'djto. t n.

In my co-pending application Serial N-o. 215,787 filed 'August 27, 1927,;1 disclosed a construction wherein the advantageous qualities of oil had been attained in a highly efiicient mannnand wherein the proportion of'oil to'carrying medium'in' a comparatively large thickness of insulating layer had been materially increased. More particularly,"I disclosed a composite insulating layer, the main portion of which'consisted ofa 'rela tively bulky and porous material, this material being sandwiched between two relatively dense and thin outer layers of paper or the like.

One of the objects of my present inven tion is to attain the advantageous results of the construction illustrated and described in said pending application. A more particular object is to attain these results without resorting to the employment of a composite insulating layer of the character therein mentioned.

Briefly. I have provided a condenser wherein a relatively porous and highly absorbent material may be satisfactorily employed by itself without sandwiching the same between layers of relatively dense paper or the like. For example, in accordance with my present inventioml may employ material of the relatively coarse and porous characterof woven or tei-t'tile material, such as cheesecloth'orthe like. In certain cases I have found it satisfactory toemploy material which is not necessarily woven, but which has the same ==i desirable qualities from the standpoint of the contemplated purpose. For example, a relatively thick and coarse unsized paper may be employed, or a paper deliberately provided in advance with a number of openings or apertures.

Thus, although I do not entirelydispense with apositive layer of material :Eor separating the foil layers, nevertheless by my present invention I aim to approach a step nearer to the ideal type of condenser struo ture. The type of material which I employ may be genericallyreferred toas fora'mi'nous in nature. 7

In resorting to a perforated or foraminated materialit has been. necessary'tor me to provide means, for. assuring a continuous separation between the conducting layers. Inother words, although a toraminated insulating layer approaches an. ideal condition andlafiiords accommodation for a relatively greater percentage of the highly desirable dielectric'rnateria-lsuch as wax or oil, it also presents the danger: previously mentioned of havingthe cond'uctinglayers of foil contact with each'other through the perforations or toramena. In accordance with my present invention, I have obviated this difliculty by suitably proportioning the thicknesses and relative bodies of: the conducting and insulating layers, as well as by suitably providing for their respective tensions.

The manner in which I have attained the foregoing objects and such other objects as may hereinafter appear who pointed out will be'more clearly understood upon reference totheaccompanying drawing, in whicha Figure lis anenlarged cross-sectional view through a portionof a condenser body constructed inaccordance with my present invention and employing a woven material;

Figure 2 is a view similar-t0 Figure l illustrating the employmentjof a pre-perforated material of an unwoven character;

Figure 3 is a similar view illustrating the possible employment of a'suitab-le material which is neither deliberately perforated nor woven, and

Figure 4: shows a finished condenser body of the rolled type.

In Figure l, I have. shown a fragmentary cross-section through a condenser body, and have, for the sake of simplicity, illustrated onlytwo adjacent conducting layers 10 and 11. These layers may be of suitable foil, such as tin, copper, or'aluminum. Interposed between these layers I provide av foraminated material such as a woven textile 12. Ordinary cheesecloth or the like has proved to be satisfactory for this purpose. Of course, it

will be understood that a second foraminated layer of the same material on the opposite side of either of the layers 10 and 11 is provided to keep the conducting layers out of contactwhere the condenser is to be of the rolled type.

the third pl-acfthdwoven material is comparatively thick as compared with the thickness ofthe paper layer customarily employed. Inasmuch. as thebreakdown voltage of a condenser is dependent upon the space between the conducting layers, a relatively great thickness ofv the woven materialprov-id'es: for ahi'gh. breakdown voltage; 1

- If the woven material is sufiiciently thick and the spaces betweenthe strands are sufficiently small, I have found that. there is. no danger of contact between the separated foil layers. Where the material is very loosely woven, so that the ratio of space between strands to thickness of material is increased, I assuredly prevent short-circuiting by increasing the tensions. of the foil layers. during the association thereof. with the insulating layer. This tensioni may, for. example, be

maintained duringmanufacture by suitably braking the reels from which the strip material is fed to the winding mandrel or the like, and the usual sticker 20 (Figure L) which is applied to thewound body 21 after the winding procedure is completed serves to maintain the proper conditions in the finished condenser body.

In accordance with my invention, I employ a woven material which is as 'loosely'woven as possible so that most of the space between the foil layers is occupied by the dielectric material, such as oil. In this way, I approach the ideal constuct-ion wherein such space is occupied entirely by the dielectric material.

In Figure 2 I have shown the possible employment between foil layers 13 and 14 of an unwoven material 15 purposely provided in advance with a series of perforations or foramena 16. For example, a material such as coarse unsized and relatively thick paper has proven satisfactory, and its characteristics are very similar to the characteristics previously mentioned in connection with the woven material 12. The coarse nature of the paper renders it highly absorbent so that it may accommodate a very large amount of the impregnating medium such as oil. The thickness of the paper provides for a maximum distance between foil layers, thereby increasing the breakdown voltage. The openings 16 afford accommodation for tree oil, where the latter is the medium employed, and these openings are made as large as possible with relationship to the maximum permissible tension that may beapplied to the foil layers 13 and 14.

Instead of tensioning the foil layers, I have found it satisfactory to increase their thicknesses, thereby imparting greater body to them and consequent greater resistance to buckling. I

In Fi ure 3 I have shown the possible employment between foil layers 17 and 18 of a relatively thick layer 19 of coarse unsized paper which has not been previously perforated. The employment of such unperforated paper is capable in a measure of fulfilling the general aim of the present invention, provided that the texture of the paper is sufficiently coarseso that it'may be reasonably termed a foraminouslayer.

Obviously, where perforations are absent, as in Figure 8, the thickness and tension of each foil layer may be correspondingly reduced. a i i It will thus be seen that I have provided a condenser and a method of constructing the same whereby thecost of manufacture is materially reduced, and wherebythe advantageous qualities of oil may be efliciently resorted to. i To demonstrate by means of fig ures the advantageous results achieved by my present invention, I will point out that a theoretical condenser having nothing but oil between its foil layers might be assumed to have a breakdown voltage of approximately thirty thousand volts. Where paper is, employed in the customary and well known manner, the breakdown voltage may be in the neighborhood of forty thousand volts, but it would be unsafe to operate thecondenser 'under a continuing voltage greater than twenty thousand volts.v Thus, during a twenty thousand volts safe operation, the life of the condenser might be approximately ten years. In the theoretical condenser, however, the life'of the condenser would be practically unlimited even during a continuous operation under as much as twenty-five thousand volts. The reason for this lies in condenser would be caused only by oxidation raminous material, such as cheesecloth, preof the oil, whereas a breakdown where paper is employed would be caused most probably I by a breaking or tearing of the paper due to I leakage currents.

It is obvious that the employment of a foperforated highly absorbent paper or the I like, approaches a condition equivalent to the theoretical condenser; and I have, as a matter of fact, found by tests that the condensers constructed in accordance with'the present have hereinillustrated the invention as it is applied to a condenser of the rolled type,

nevertheless the invention is not necessarily restricted to this particular type of condenser, and may be applied with almost equal facility to condensers of the stacked type, in

which case suitable clamping devices engaging either the edges of the foil strips or other portions of such strips would serve to hold the strips in suflicient tensionto prevent any buckling of the strips through the spacing layers.

The details herein described and illustrated are intended to serve in explanation of the be interpreted as illustrative and not in a limiting sense, unless the prior art should require such limited interpretation. 'Having thus described my invention and illustrated its use, what I claim as new and desire to secure by Letters Patent is V 1. An electrical condenser comprising a set of alternately arranged conducting and foraminated insulating layers, the latterbeing in direct contacting sandwiched relationship to the conducting layers, and the conducting layers being sufliciently tensioned to prevent buckling thereof.

2. In an electrical condenser, the combination of a pair of foil conducting layers and.

arranged, metallic foil conducting strips and insulating strips, the insulating strips com prising relatively thick and highly absorbent unsized paper having perforations there- 'through, and the foil strips being sufliciently tensioned to' prevent buckling thereof through the perforations of the insulating f strips. the ract that a breakdown in the theoretical I In witness whereof, I have signed this specification this 10th day of December, 1928. HAROLD I. DANZIGER.

nature of my invention and are therefore to 

